초록
Background: mcl-PHA biosynthesis by Pseudomonas citronellolis from tallow-based biodiesel as inexpensive carbon feed stock was accomplished. Fermentation protocols, kinetic analysis, an efficient product recovery strategy, and a detailed product characterization are presented. Results: A maximum specific growth rate, μ<SUB>max.</SUB> of 0.10 and 0.08h<SUP>-1</SUP>, respectively, was achieved in two different fermentation set-ups. Volumetric productivity for mcl-PHA amounted to 0.036g/Lh and 0.050g/Lh, final intracellular PHA contents calculated from the sum of active biomass and PHA to 20.1 and 26.6wt.%, respectively. GC-FID analysis showed that the obtained biopolyester predominantly consists of 3-hydroxyoctanoate and 3-hydroxydecanoate, and, to a minor extent, 3-hydroxydodecanoate, 3-hydroxynonanoate, 3-hydroxyhexanoate, and 3-hydroxyheptanoate monomers. This was confirmed by <SUP>1</SUP>H- and <SUP>13</SUP>C NMR, also evidencing the occurrence of low quantities of unsaturated and 3-hydroxyvalerate building blocks. High purity of the recovered materials was proofed by elemental analysis. Regarding the results from thermogravimetric analysis, differential scanning calorimetry and molecular mass determination, results were in a range typical for this type of PHA (1st fermentation: decomposition temperature T<SUB>d</SUB>=296<SUP>o</SUP>C, peak of melting range T<SUB>m</SUB>=48.6<SUP>o</SUP>C; glass transition temperature T<SUB>g</SUB>=-46.9<SUP>o</SUP>C, degree of crystallinity X<SUB>c</SUB>=12.3%, M<SUB>w</SUB>=66,000, M<SUB>n</SUB>=35,000, dispersity index P<SUB>i</SUB>=1.9; 2nd fermentation: T<SUB>d</SUB>=295<SUP>o</SUP>C, T<SUB>m</SUB>=53.6<SUP>o</SUP>C, T<SUB>g</SUB>=-43.5<SUP>o</SUP>C, X<SUB>c</SUB>=10.4%, M<SUB>w</SUB>=78,000, M<SUB>n</SUB>=196,000, P<SUB>i</SUB>=2.5).